At a sugar refinery, the operator determined the presence of legionella in its cooling circuit; results indicated a high rate of bacteria. The operator immediately decided to notify personnel and mark off the zone around the base of the cooling towers, in addition to treating the cooling circuit with a biocide and dispersant. The work inspection banned access to this zone near the cooling towers as well as the building housing vacuum pumps and circulation pumps for anyone not wearing a breathing mask designed for biological risks. Access was only authorised for trained staff equipped with a self-breathing apparatus. For this purpose, a special instruction was to be drafted. Facility personnel were informed of the risk related to legionella to avoid unwarranted concern, as was the case during this incident. For the current sugar production run, the refinery manager had already adopted preventive measures relative to Legionnaire’s disease. For subsequent runs, a presentation favouring the systematic implementation of these measures was planned.